Hibernate Session 3
- 1. Transaction and Concurrency Session - III
- 2. TRANSACTION – FAST BRUSH UP Atomicity – refers to the ability that, either all of the tasks of a transaction are performed or none of them are. Consistency - refers to the database being in a legal state when the transaction begins and when it ends. Isolation - refers to the ability of the application to make operations in a transaction appear isolated from all other operations. Durability - refers to the guarantee that once the user has been notified of success, the transaction will persist, and not be undone.
- 3. Programmatic Transaction Demarcation java.sql.Connection – To be avoid in Hibernate application as it binds to plain JDBC environment. javax.transaction.UserTransaction – should be used in Java EE application/JTA supported environment. org.hibernate.Transaction – Unified transaction demarcation for Hibernate application; works both in managed and non-managed.
- 4. Transactions & Exceptions Hibernate 3.x exceptions are typed runtime exceptions. HibernateException – generic exception. JDBCException – thrown by hibernate internal JDBC layer. Subtypes – JDBCConnectionException SQLGrammarException LockAcquisitionException DataException ConstraintViolationException
- 5. Hibernate typed exceptions All exceptions throws by Hibernate are RuntimeException and are fatal exceptions. It is the programmers responsibility in non-managed environment to rollback the transaction in case of exceptions.
- 6. Concurrency Strategies Hibernate never changes the Isolation level of connections obtained from Application server. Optimistic Versioning – Numeric Version Field Timestamp based Without an additional field (not recommended) Pessimistic Achieved with LockMode.UPGRADE or LockMode.UPGRADE_NOWAIT
- 7. Hibernate - LockMode LockMode.NONE - Don’t go to the database unless the object isn’t in any cache. LockMode.READ - Bypass all caches, and perform a version check (if applicable) to verify that the object in memory is the same version that currently exists in the database. LockMode.UPDGRADE - Bypass all caches, do a version check (if applicable), and obtain a database-level pessimistic upgrade lock, if that is supported. Equivalent to LockModeType.READ in Java Persistence. This mode transparently falls back to LockMode.READ if the database SQL dialect doesn’t support a SELECT ... FOR UPDATE option.
- 8. LockMode.UPDGRADE_NOWAIT - The same as UPGRADE, but use a SELECT ... FOR UPDATE NOWAIT, if supported. This disables waiting for concurrent lock releases, thus throwing a locking exception immediately if the lock can’t be obtained. LockMode.FORCE - Force an increment of the objects version in the data-base, to indicate that it has been modified by the current transaction. Hibernate – Lock Mode (Cont..)